Fractionating coal liquefaction products with light organic solvents

ABSTRACT

Coal liquefaction products are separated into a plurality of fractions of varying softening points and molecular complexity by treatment with light organic solvents having critical temperatures below 800* F. under elevated temperature and pressure conditions. In one variant, coal is liquefied employing selected light organic solvents which are suitable for both liquefaction and fractionation, and thereafter the coal liquefaction products are separated into a plurality of fractions by treatment with the solvent contained in the resultant solution. Preferred solvents for liquefying coal include pyridine and benzene, and preferred fractionating solvents include pyridine, benzene and hexane. In a preferred variant, a solvent phase is recovered directly from the final fractionating stage and is passed in heat exchange relationship with solvent-rich streams to preceding fractionating stages to recover the heat content and provide cooled solvent for recycle. The invention further provides a method of separating finely divided insoluble material derived from coal during liquefaction thereof from an organic-solvent solution of coal liquefaction products.

United States Patent [72] Inventor Jack W. Roach Oklahoma City, Okla.[21] AppLNo. 1,818 [22] Filed Jan. 9, 1970 [45] Patented Sept. 21,197][73] Assignee Kerr-McGee Corporation Oklahoma City, Okla.

[54] FRACTIONATING COAL LIQUEFACTION PRODUCTS WITH LIGHT ORGANICSOLVENTS 28 Claims, 2 Drawing Figs.

[52] US Cl 208/8 [5!] Cl0g 1/00 [50] Field of Search 208/10 [56]References Cited UNITED STATES PATENTS 2,221,866 ll/l940 Dreyfus 208/82,913,397 ll/l959 Murray et al. 208/8 2,202,901 6/! 940 Dreyfus 208/82,9l3,388 ll/l959 Howell et al 208/8 Primary Examiner-Delbert E. GantzAssistant Examiner Veronica OKeefe Attorney-Shanley and O'Neil ABSTRACT:Coal liquefaction products are separated into a plurality of fractionsof varying softening points and molecular complexity by treatment withlight organic solvents having critical temperatures below 800 F. underelevated temperature and pressure conditions. In one variant, coal isliquefied employing selected light organic solvents which are suitablefor both liquefaction and fractionation, and thereafter the coalliquefaction products are separated into a plurality of fractions bytreatment with the solvent contained in the resultant solution.Preferred solvents for liquefying coal include pyridine and benzene, andpreferred fractionating solvents include pyridine, benzene and hexane.In a preferred variant. a solvent phase is recovered directly from thefinal fractionatin g stage and is passed in heat exchange relationshipwith solventrich streams to preceding fractionating stages to recoverthe heat content and provide cooled solvent for recycle. The inventionfurther provides a method of separating finely divided insolublematerial derived from coal during liquefaction thereof from anorganic-solvent solution of coal liquefaction products.

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ATTORNEYS FRACTIONATING COAL LIQUEFACTION PRODUCTS WITH LIGHT ORGANICSOLVENTS BACKGROUND OF THE INVENTION This invention broadly relates to amethod of separating coal liquefaction products into a plurality offractions employing light organic fractionating solvents under elevatedtemperature and pressure conditions. The invention further relates to anovel process for liquefying coal and fractionating the resultantproducts, and a method of separating finely divided insoluble materialfrom a solution of coal liquefaction products.

The potentially soluble substances in fossilized carbonaceous materialssuch as coal are composed largely of high molecular weightthree-dimensional cyclic structures which contain predominantlysix-membered rings. For example, coal contains bitumen and humin, whichhave large, flat, aromatic lamellar structures that differ in molecularweight, degree of aromaticity, oxygen content, nitrogen content andcross-linking, volatile matter, fusain, mineral matter, sulfur andmoisture. The sulfur content may be present as pyritic sulfur,

inorganic sulfates, and/or organic sulfur compounds.

The mineral matter remains behind as ash when the coal is burned andfusain, which is a mineral charcoal, is consumed during burning at hightemperatures in the presence of sufficient oxygen for completecombustion. The presence of sulfur in the coal in substantial quantitiesresults in contamination of the atmosphere with oxides of sulfur uponcombustion, and highly corrosive sulfurous acid and/or sulfuric acid isproduced therefrom upon reaction with atmospheric moisture. As a result,air pollution regulations in metropolitan areas often require that thesulfur content of fuels be reduced so as to control atmosphericpollution. The mineral content of the coal may be ll5 percent by weightor higher in some instances, and this reduces the B.t.u. value of theraw coal per unit weight and increases transportation costs. There is anadditional cost when the coal is burned as the ash residue must beremoved and disposed of in some manner.

The presence of mineral matter, fusain and sulfur in substantialquantities also reduces the value of the coal for specialized uses. Forexample, if these substances are removed prior to coking, the deashedcoal thus produced may be used for preparing high purity anode cokewhich has a substantially higher value than the usual impure cokeproduced from raw coal.

For the above and other reasons, it is desirable to reduce the mineralmatter, fusain and sulfur contents of coal. One process presently usedfor removing these substances involves solvation or liquefaction ofdesirable coal constituents such as bitumen and humin in an organicsolvent to produce a solution of coal liquefaction products containingsuspended finely divided insoluble material. Thereafter, the undesirableinsoluble constituents such as mineral matter, fusain and inorganicsulfur are separated from the solution prior to recovery of the deashedcoal liquefaction products.

The methods available heretofore for separating finely divided insolublematerial from a solution of coal liquefaction products have left much tobe desired. For example, gravity settling has a number of disadvantagesdue in part to the low settling rates encountered under ambientconditions of temperature and pressure, and especially in instanceswhere the solution is somewhat viscous in nature. Filtration methodsalso have disadvantages as the solution is often viscous at roomtemperature and must be heated to obtain sufficiently fast filtrationrates. Plugging of the filter pores with finely divided insolubleconstituents is an additional problem. In instances where the viscosityof the solution is sufficiently low, centrifuging is usuallysatisfactory insofar as the physical separation of the solids from thesolution is concerned. However, centrifuging equipment is costly and itis difficult to remove the lighter micron-sized particles. As a resultof the above and other deficiencies, there has not been an entirelysatisfactory method available heretofore for separating suspended finelydivided insoluble materials from an organic-solvent solution of coalliquefaction products.

The solvation of coal in an organic-solvent produces a mixture of coalliquefaction products which differ greatly with respect to theirchemical and physical properties. For example, the liquefaction productsmay vary from low boiling liquids to solids which are soluble in theorganic solvent and have softening points of 300400 F. and higher. Thelow boiling liquid products may be recovered by distillation, but amethod has not been available heretofore for separating normally solidcoal liquefaction products into a plurality of fractions having desiredsoftening points or other physical and/or chemical characteristics. Asatisfactory fractionating method would be very useful as coalliquefaction products with widely differing properties could be producedfor specific end uses.

The present invention provides an efficient method of separating ashconstituents from previously prepared coal liquefaction products, and/orfractionating previously prepared deashed coal liquefaction productsinto a plurality of fractions. Additionally, it is also possible toliquefy coal employing certain light organic solvents of the invention,and to thereafter deash and/or fractionate the coal liquefactionproducts in the same solvent. The liquefying and fractionating stepsinvolve the use of large quantities of light organic solvent andheretofore it has been necessary to recover the solvent from the finalfractionating stage by flashing and condensation of the solvent vapor.This prior art method of solvent recovery involves the use of expensiveequipment with high operating costs as the utility requirements areexcessive. The present invention overcomes this disadvantage byproviding for the recovery of the solvent directly from the lastfractionating stage whereby it may be heat exchanged with incomingstreams to recover heat and produce a cooled stream of solvent forrecycle.

It is an object of the present invention to provide a novel method ofseparating coal liquefaction products into a plurality of fractionsemploying selected light organic solvents.

It is a further object to provide a novel method of separating coalliquefaction products into a plurality of fractions wherein the solventmay be recovered directly from the final fractionating stage and passedin heat exchange relationship with incoming streams to precedingfractionating stages to recover the heat content.

It is a further object to provide a novel process for liquefying coalemploying selected light organic solvents, and then separating the coalliquefaction products in the solution thus produced into a plurality offractions.

It is a further object to provide a novel method of separating suspendedfinely divided insoluble material derived from coal during liquefactionthereof from an organic-solvent solution of products of coalliquefaction.

Sill other objects and advantages of the invention will be apparent tothose skilled in the art upon reference to the following detaileddescription and the examples.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B of the drawingsillustrate one presently preferred arrangement of apparatus for use inpracticing the invention.

FIG. 1B is a continuation of FIG. 1A.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING PREFERRED VARIANTSTHEREOF The process of the present invention provides a method wherebyliquefied coal dissolved in a light-fractionating solvent is introducedinto a deashing-fractionating vessel under temperature and pressureconditions such that the solvent density of the light-fractionatingsolvent is about0.350.55 g./cc. and sufficiently low to cause therejection or separation of a small amount of the heavy liquefied coalconstituents. The lighter solvent-rich liquefied coal solution exitingfrom the deashing-fractionating vessel may then be introduced into atleast one fractionating vessel, in the last of which the temperature andpressure of the solution are adjusted to give a solvent density of about0.15-0.20 g./cc. to yield a fluid bottom fraction comprising theresidual dissolved coal and a lighter solvent phase which may bewithdrawn and recycled for heat recovery and reuse. in those instanceswhere more than one fractionating vessel is employed, the solventdensities prevailing in the intermediate fractionating vessels aredecreased progressively from the solvent density existing in thedeashingfractionating vessel to the solvent density existing in thefinal fractionating vessel to thereby provide a succession of heavy coalfractions of decreasing softening point and a succession ofcorrespondingly lighter solvent-rich phases. In one variant of theinvention, the deashing-fractionating vessel and all subsequentfractionating vessels may be operated at a pressure which is at or belowthe critical pressure of the fractionating solvent provided that thepressure, temperature and enthalpy are controlled whereby the solventdensities set forth herein are maintained.

Referring now to the drawings, a selected light organic solvent to bedefined more fully hereinafter is transferred by pump 10 from solventsurge vessel 11 to mixer 12 via conduit 14 at a rate controlled by valve15. Makeup solventis supplied to vessel 11 as required via conduit 8 ata rate controlled by valve 9. in the variant to be presently described,which includes liquefying the coal and thereafter fractionating theliquefaction products in the same solvent, finely divided raw coal instorage vessel 16 is passed into mixer 12 via conduit 17 at a ratedetermined by meter 18. The relative feed rates of solvent and coal maybe controlled so that the weight ratio of solvent to coal in mixer 12 isbetween about 1:1 and 20:1, and preferably between about 2:1 and :1. Thebest results are usually obtained when the weight ratio of solvent tocoal is approximately 3:l.

The coal and solvent in mixer 1 1 are agitated with a motordrivenagitator l9, and the slurry thus prepared is withdrawn via conduit 20and transferred by pump 21 to gas-fired heater 22 where the slurryflowing in coil 23 is heated to an elevated temperature which preferablyclosely approximates the desired initial temperature of solvation. Inthe variant presently described, valve 24 in conduit 25 is closed andvalve 26 in conduit 27 is open, and the heated slurry is withdrawn viaconduit 27 and passed to liquefier 28. While it is not essential, it isusually preferred to carry out the liquefaction in the presence of addedgaseous hydrogen. When gaseous hydrogen is added, it may be passed intothe slurry flowing in conduit 20 upon opening valve 29 in conduit 30.

The liquefier 28 preferably operates under a high superatmosphericpressure which is determined by the overpressure of gaseous hydrogenwhen present, the vapor pressure of the solvent at the operatingtemperature, and/or the hydraulic pressure applied by pump 21. Theliquefaction temperature is determined by the initial temperature of theslurry flowing in conduit 27 and by the temperature control fluid whichis supplied to coil 31 via conduit 32 at a rate controlled by valve 33and withdrawn via conduit 34. The solvent is contacted with the coalunder the temperature and pressure conditions existing in the liquefier28 for a sufficient period of time to solubilize a substantial amount ofextractable carbonaceous content thereof, and to produce a solution ofcoal liquefaction products which contains suspended finely dividedfusain, mineral ash and other insoluble constituents. The resultantsolution usually contains relatively large amounts of dissolved normallysolid liquefaction products of widely varying softening points, and inmany instances little or no low boiling normally liquid products. Thesolution is preferably but not necessarily substantially saturated withrespect to the dissolved coal liquefaction products under thetemperature and pressure conditions existing in liquefier 28, i.e., atthe solvent density in liquefier 28.

The solution containing insoluble constituents is withdrawn fromliquefier 28 via conduit 35 and is introduced into bulk insoluble coalseparator 36. At least 95 percent by weight, and

usually more than 99 percent by weight, of the insoluble constituentsseparate as a heavy slurry phase 37 which is sufficiently fluid underthe existing temperature and pressure conditions to be withdrawn viaconduit 39 at a rate controlled by valve 40. The lighter phase 38containing dissolved coal possessing less than l percent by weight ofash is withdrawn via conduit 41 and is passed through heat exchanger 46.The solution flowing in conduit 41 when withdrawn from separator 36 isat approximately the same temperature and pressure as exist in liquefier28 and the excess heat content thereof is recovered by heat exchange inheat exchanger 46 with cold solvent flowing in conduit 14. The coldsolvent is heated to an elevated temperature in heat exchanger 46 and isthen passed into mixer 12 as previously described, and thus the slurryflowing in conduit 20 is likewise at an elevated temperature. Thesolution flowing in conduit 41 downstream of pressure reduc ing valve 44is at approximately the desired temperature of operation ofdeashing-fractionating vessel 47, and the temperature of the solutionflowing in conduit 41 may be controlled at a desired level by passingall or a portion thereof around heat exchanger 46 via conduit 42 at aratio determined by valves 43 and 48. The pressure on the solutionflowing in conduit 41 is reduced while passing through pressure-reducingvalve 44 to approximately the desired pressure of operation of vessel47, and the solution is then introduced into gas separator 61. Hydrogen,gaseous hydrocarbons and other gaseous constituents are separated fromthe solution and withdrawn via conduit 62 at a rate controlled by valve63. The degassed solution is withdrawn from gas separator 61 via conduit49 and normally open block valve 45. The temperature and pressureconditions selected for operation of deashing-fractionating vessel 47are such that the solvent density of the light organic solvent is about0.35-0.55 g./cc. and sufficiently low to cause the rejection orseparation of a small amount of the heavy liquefied coal constituents.While the mechanism is not fully understood, it is believed that thecoal liquefaction products thus rejected from the solution tend to coatthe micron-sized particles of insoluble material in the solution. Thiscauses the surface of the particles to be tacky, and enlarges theparticles somewhat so that they are much easier to agglomerate thanwould otherwise be true. The amount of coal liquefaction productsseparated as a heavy phase in vessel 47 need be only sufficient to coatthe insoluble particles and, with the attendant solvent, aid in theagglomeration and fluxing thereof, and usually is no more than about 1or 2 times the weight of insoluble material. However, substantiallylarger amounts of coal liquefaction products, such as 3-5 times theweight of insoluble material, may be separated if desired, as this doesnot interfere with the removal of the ash.

The solution containing finely divided insoluble constituents is passedvia conduit 49 to header 50. The header 50 is positioned indeashing-fractionating vessel 47 a substantial distance beneath theinterface 52 between the relatively heavy slurry phase 53 and thelighter clarified solution of coal liquefaction products 54, and it isprovided with a plurality of spaced outlets 51. The fluidlike slurrylayer 53 in the bottom portion of vessel 47 contains suspended mineralash, fusain, and other insoluble material in finely divided form whichis fluxed with solvent and coal liquefaction products, and it iswithdrawn via conduit 55 at a rate controlled by valve 56, or byoperation of a pump which controls the volume. The slurry 53 iswithdrawn at a rate to maintain the interface 52 substantially above theoutlets 51 on header 50. The solution flowing in conduit 49 is at anelevated temperature and has a low viscosity, and the particles ofcoated suspended material settle out rapidly when the solution is passedinto vessel 47. While the mechanism is not fully understood, it isbelieved that injecting the solution into the heavy slurry layer 53 andpassing the solution upward therethrough into the clarified phase 54also causes the micron-sized solid particles of insoluble material toagglomerate into larger particles more rapidly and completely, and thelarger particles in turn settle much faster. Unexpectedly, the presenceof the slurry layer and passing the solution therethrough aids incoating the individual particles of micronrsized solids and in theagglomeration thereof to produce much heavier particles than wouldotherwise be possible. As a result, the lighter clarified phase 54 inthe upper portion of vessel 47 is substantially free of insolublematerial and it does not require filtering or centrifuging to remove thelast traces of solids. The vessel 47 may be maintained at the desiredoperating temperature by passing a heat exchange fluid to coil 57 viaconduit 58 at a rate controlled by valve 59 and withdrawing it viaconduit 60.

The clarified coal solution 54 is withdrawn from the top of vessel 47via conduit 65 at a rate to provide a sufficient residence time toassure settling of the insoluble material, such as l-30 minutes andpreferably about 5-15 minutes. The clarified solution 54 is then passedthrough heat exchanger 66 in heat exchange relationship with a warmsolvent stream which is being recycled through conduit 64 to solventsurge vessel 11. The solution is withdrawn from heat exchanger 66 at asubstantially higher temperature and preferably at a temperature closelyapproximating the desired operating temperature for fractionating vessel67, and is then introduced into vessel 67 via conduit 65. The solventdensity existing in vessel 67 is substantially less than that existingin vessel 47 due to the higher operating temperature and the slightlylower pressure resulting from the drop in line and heat exchangerpressure. The differential in the solvent density is sufficiently largeto cause a fluidlike fraction 72 of heavy coal liquefaction products toseparate from the solvent rich lighter phase 75 of residual coalsolubilization products. The vessel 67 is maintained at a uniformoperating temperature which is sufficiently elevated to permit aliquid-to-liquid bulk interface 76 to form between heavy fraction 72 andsolvent rich phase 75. The temperature is maintained at the desiredlevel by means of a heat exchange fluid fed to coil 68 via conduit 69 ata rate controlled by valve 70 and withdrawn via conduit 71. Thetemperature and pressure conditions existing within vessel 67 areselected to provide a solvent density whereby a desired percentage ofthe heaviest material dissolved in the solution is separated in the formof a fluidlike heavy phase 72. The heavy phase 72 contains sufficientlight solvent to lower the viscosity and allow it to be withdrawn viaconduit 73 upon opening valve 74 without plugging the same. The lightsolvent content of the withdrawn heavy phase 72 can be recovered byflashing and condensation of the vapor to produce liquid light solventfor recycling in the process. The residue remaining after flashing thesolvent is a hard friable deashed heavy coal fraction having a softeningpoint of about 400 F. or higher.

The solvent-rich phase 75 containing residual liquefied coal products iswithdrawn from the top of vessel 67 via conduit 77 and passed throughheat exchanger 78 in heat exchange relationship with the warm solventstream flowing in conduit 64. The solvent rich phase 75 is withdrawnfrom heat exchanger 78 at a higher temperature and preferably at atemperature closely approximately the desired operating temperature forfractionating vessel 79, and is introduced into vessel 79 via conduit77. The solvent density existing in vessel 79 is substantially less thanthat existing in vessel 67 due to the higher operating temperature andthe slightly lower pressure level resulting from the drop in line andheat exchanger pressure. The differential in solvent density betweenvessels 67 and 79 is sufficiently large to cause a fluidlike heavyfraction 80 of residual liquefied coal products to precipitate from thelighter solvent rich phase 81. The vessel 79 is maintained at a uniformoperating temperature which is sufficiently elevated to permit aliquid-to-liquid bulk interface 82 to form between heavy fraction 80 andthe solvent-rich phase 81. The temperature is maintained at the desiredlevel by means of heat exchange fluid fed to coil 83 via conduit 84 at arate controlled by valve 85 and withdrawn via conduit 86. Thetemperature and pressure conditions existing within vessel 79 areselected so that a desired percentage of the liquefied coal products ofintermediate softening point dissolved in solvent rich phase 75 areseparated. The heavy phase 80 contains some solvent and has asufficiently low viscosity to be withdrawable via conduit 87 uponopening valve 88 without plugging the same. The solvent content may berecovered by flashing and condensation of the vapor to produce liquidlight solvent for recycling in the process. The residue is a normallysolid deashed coal product. lt is understood that the residue withdrawnfrom successive fractionating vessels will have successively lowersoftening points. In many instances, the residue obtained from phasewill have a softening point below 400 F. and usually has a softeningpoint of about 200 F.400 F.

The solvent rich phase 81 containing dissolved light liquefied coalproducts is withdrawn from the top of vessel 79 via conduit 90 andpassed through heat exchanger 91 in heat exchange relationship with thewarm solvent stream being recycled through conduit 64. The solvent-richphase 81 is withdrawn from heat exchanger 91 at a higher temperature,passed to gas-fired heater 93 where it is heated to a temperatureclosely approximating the desired operating temperature forfractionating vessel 92, and introduced into vessel 92 via conduit 90.The solvent density existing in vessel 92 is substantially less thanthat existing in vessel 79 due to the higher operating temperature andthe slightly lower pressure level resulting from the drop in line andheat exchanger pressure. The solvent density differential betweenvessels 79 and 92 is sufficient to cause a fluidlike fraction of theremaining liquefied coal products 94 to separate from the lightersolvent phase 95. The vessel 92 is maintained at a uniform operatingtemperature which is sufficiently elevated to reduce the solvent densityto a level that causes the solvent to separate from the remainingdissolved liquefied coal products. The operating temperature is alsosufficiently elevated to permit a liquid-toliquid bulk interface 96 toform between the separated fraction 94 and the solvent phase 95. Theuniform operating temperature is maintained by means of a heat exchangefluid fed to coil 97 via conduit 98 at a rate controlled by valve 99 andwithdrawn via conduit 100. The separated fraction 94 contains sufficientsolvent to lower the viscosity whereby it is withdrawable via conduit101 upon opening valve 102 without plugging the same. The solventcontent of the withdrawn fraction 94 may be recovered by flashing andthe vapor condensed to produce liquid solvent for recycling and adeashed coal fraction which is semisolid to liquid at room temperature.The hot light organic solvent phase is withdrawn from the top of vessel92 via conduit 64 and passed successively through heat exchangers 91, 78and 66 in heat exchange relationship with the relatively coolsolvent-rich phases flowing in conduits 90, 77 and 65, respectively. Thesolvent-rich phases thereby are heated. The solvent flowing in conduit64 downstream of heat exchanger 66 is further cooled in heat exchanger103 by means of a coolant supplied via conduit 104 at a rate controlledby valve 105 and withdrawn via conduit 106. This method of operationallows cool solvent to be recovered directly from the solution ofliquefied coal products flowing in conduit 90 without flashing andcondensation of the solvent vapor. As a result, the cost of solventrecovery for recycle is much lower. it is also possible to recover theheat content of the phased out hot heavy phases 53, 72, 80 and 94 andthis further reduces the overall costs.

The variant previously discussed is concerned with liqucfying coal toproduce a solution of coal liquefaction products in light organicsolvent, and thereafter fractionating the products into a plurality offractions employing the same solvent for both steps. The presentinvention is also useful for fractionating coal liquefaction productsrecovered from the liqucfying solvent with or without prior removal ofthe insoluble constituents. The products are usually recovered in theform of a normally solid-friable material which is capable of beingdissolved in light organic-fractionating solvents. Thus, it is possibleto liquefy the coal in a highly efficient heavy organic solvent, recoverthe coil liquefaction products from the resultant solution by flashingoff the solvent, and then remove the insoluble constituents andfractionate the coal liquefaction products in accordance with thepresent invention.

Referring again to FIGS. 1A and 1B of the drawings, previously preparedfinely divided normally solid coal liquefaction products substantiallyfree of the liquefying solvent are withdrawn from storage vessel 16 andpassed into mixer 12 via conduit 17 at a rate determined by meter 18.Light organic fractionating solvent is introduced into mixer 12 viaconduit 14 at a rate controlled by valve 15. The relative feed rates ofsolvent and coal liquefaction products are controlled so that the weightratio of solvent to coal liquefaction products existing in mixer 12 isbetween about 2:1 and 20:1 and preferably between about 3:1 and 5:1. Themixture thus produced is withdrawn from mixer 12 via conduit 20 andtransferred by pump 21 to gas fired heater 22 where it is heated in coil23 to an elevated temperature which preferably closely approximates theoperating temperature of vessel 47. The coal liquefaction productsdissolve in the light organic fractionating solvent and, upon closingvalves 26, 43 and 48 and opening valve 24, the solution is passed viaconduits 25 and 49 to header 50 and introduced into vessel 47 throughoutlets 51.

The vessel 47 may be operated as previously described to removeinsoluble constituents which are withdrawn as a fluidlike phase viaconduit 55. In instances where the coal liquefaction products have beenpreviously deashed, very little if any insoluble material is removed butpassing the solution through vessel 47 assures that a small amount ofinsoluble material is not present in the heavy coal fraction produced invessel 67. The coal liquefaction products contained in the clarifiedsolution 54 withdrawn via conduit 65 are fractionated in vessels 67, 79and 92 to produce heavy, intermediate and light fractions which arewithdrawn via conduits 73, 87 and 101, respectively, in the mannerpreviously discussed. The light organic-fractionating solvent phase 95is withdrawn via conduit 64 and passed through heat exchangers 91, 78,66 and 103 to recover the heat content and produce cool solvent forrecycle as previously discussed.

The carbonaceous material fed to mixer 12 and liquefied in liquefier 28may be coal, which preferably is of a rank lower than anthracite, suchas subanthracite, bituminous, subbituminous, and lignite or brown coal.Peat also may be used in some instances. The particle size of the coalmay vary over wide ranges and in general the particles only need besufficiently small to be slurried in the solvent and pumped. Forexample, the coal may have an aver particle size of one-fourth inch indiameter or larger in some instances, and as small as 200 mesh (Tylerscreen) or smaller. The most practical particle size is usually between30 mesh and l mesh as less energy is required for grinding and yet theparticles are sufficiently small to achieve an optimum rate ofliquefaction. The particle size is not of great importance, providedextremely large particles are not present as the solvent penetrate thecoal particles and the extractable constituents are liquefied rapidly.

Light organic solvents having critical temperatures below 800 F., andpreferably below 750 F., are employed for liquefying and/orfractionating the coal. While solvents broadly falling in thisclassification and as further defined hereinafter are suitable for useas fractionating solvents, not all are suitable for liquefying the coal.Light organic solvents useful for both liquefying the raw coal andfractionating the coal liquefaction products comprise one or moresubstances selected from the following groups:

1. Hydrocarbons:

a. Aromatic hydrocarbons having a single benzene nucleus and preferably6-9 carbon atoms, such as benzene, toluene, 0-, m-, and pxylene, ethylbenzene, npropyl or isopropyl benzene, and monocyclic aromatichydrocarbons in general having normal boiling points below about 310 F.,and

. Cycloparaffin hydrocarbons which preferably contain 4-9 carbon atoms,such as cyclobutane, cyclopentane, cyclohexane, cycloheptane, andnonaromatic monocyclic hydrocarbons in general having normal boilingpoints below about 310 F.

2. Amines, including the following:

a. Mono-, di-, and tri-open chain amines which preferably contain about2-8 carbon atoms, such as ethyl, propyl, butyl, pentyl, hexyl, heptyl,and octyl amines;

b. Carbocyclic amines having a monocyclic structure and preferablycontaining approximately 6-9 carbon atoms, such as aniline and its loweralkyl homologs wherein the alkyl groups contain about 13 carbon atomsand up to 3 alkyl groups are present on each monocarbocyclic structure;and

c. Heterocyclic amines and preferably those containing about 5-9 carbonatoms such as pyridine and its lower alkyl homologs wherein the alkylgroups contain approximately l4 carbon atoms and up to three alkylgroups are present on each hetercyclic structure.

3. Phenol and its lower alkyl homologs, and preferably phenols having6-9 carbon atoms. The alkyl groups may contain, for example, 1-3 carbonatoms and up to three alkyl groups may be present on each phenolicnucleus.

Additional light organic solvents suitable as fractionating solvents butwhich are not generally suitable as liquefaction solvents include one ormore substances from the following groups:

4. Open chain mono-olefin hydrocarbons having normal boiling pointsbelow about 310 F. and preferably con taining about 4-7 carbon atoms,such as butene, pentene, hexene, and heptene, and

5. Open chain saturated hydrocarbons having normal boiling points belowabout 3 l0 E. and preferably containing about 5-8 carbon atoms such aspentane, hexane, heptane and octane.

Pyridine and benzene are usually the preferred solvents for liquefyingcoal and pyridine, benzene and hexane for fractionating the coalliquefaction products. Other preferred solvents include light aromaticextracts of reforrnate obtained by extracting a catalytic reformate by anumber of commercial processes including the UDEX process, and aromaticor phenolic cuts in general which have critical temperatures below 800F., including those derived from the destructive distillation of coal orcoal tar and light oils. Still other commercially available mixturesincluding one or more of the foregoing classes of compounds may beemployed, and in many instances the mixture need not be purified priorto use.

The presence of added elemental hydrogen during the coal liquefactionstep is not necessary, but it is usually beneficial. When hydrogen isadded, the feed to the liquefier 28 may include 0.1-2 percent andpreferably about 0.25-1 percent by weight of hydrogen based upon theweight of the coal. The excess hydrogen which does not enter into theliquefaction reaction may be recovered from the coal liquefactionproducts and recycled if desired, and thus higher percentages than 2percent by weight of the coal may be used such as up to 5 percent byweight or more. The hydrogen content of the vapor phase in contact withthe liquid solvent phase may be about 5-50 percent and preferably isabout 10-35 percent by volume, but it may be higher or lower as desiredin a given instance. As a general rule, the higher the partial pressureof hydrogen, the faster the liquefaction reaction, as more hydrogen isavailable in the solvent for transfer to the active sites produced onthe decomposing or depolymerizing coal.

The temperature employed in operating liquefier 28 should besufficiently high to result in a fast solvation rate. The upper limit isthe temperature at which the carbonaceous material is coked and/or theorganic solvent is decomposed substantially during the period oftreatment. The temperature of liquefaction may be 550-l ,000 F. for mostsolvents and coals. ln instances where pyridine is the solvent, thepreferred temperature is usually about 650-750 F. as pyridine decomposesat temperatures of about 750800F. and higher. Benzene is much morerefractory than pyridine and temperatures above 700 F. are preferred,such as about 700800 F. or somewhat higher. The coking temperaturevaries from coal to coal, and coals having a higher rank usually have ahigher decomposition or coking temperature. Oklahoma bituminous coalcokes at about 800840 F. and the more volatile Wyoming coals at a lowertemperature such as 700-800 F. In instances where a tubular reaction isemployed and a slurry of coal is passed through the tubes on acontinuous basis, then somewhat higher solvation temperatures aresuitable due to the dynamic nature of the system. Also, the flow ratesthrough the tubes may be sufficiently fast to reduce coking on the tubesurfaces.

The liquefying solvent is contacted with the coal in liquefier 28 for asufficient period of time to solubilize a substantial amountofextractable constituents, such as about 0.2-2 hours. For economicreasons, the contact period should not be more than about 1 hour, andpreferably no more than about 0.250.5 hour. Usually more than about 50percent by weight of the coal is liquefied, and often up to 8090percent.

The minimum ratio of light fractionating solvent to coal liquefactionproducts in the resultant solution is about 2:1 by weight, and the upperlimit is practical in nature and may be as high as 20:1. There is littleimprovement in the sharpness of fractionation beyond fractionatingsolvent to coal liquefaction product ratios of 5:1 to :1, and the lowestweight ratio necessary to give a desired sharpness of fractionation ispreferred as the cost of handling the solvent increases with the amountused. Usually a fractionating solvent to coal liquefaction productsratio between about 3:1 and 5:1 is preferred.

The pressure in liquefier 28 may be between about 400 and l0,000 poundsper square inch absolute (p.s.i.a.) and should be about l,0007,000p.s.i.a. for most light organic coal liquefaction solvents. Whenpyridine is the solvent, preferably the pressure is about 3,0005,000p.s.i.a. The pressure should be sufficient to provide a solvent densityof at least 0.5 g./cc. and preferably at least 0.6 g./cc. at theexisting temperature. There is no upper limit on the solvent densityduring liquefaction as the highest solvent density that can be achievedunder practical operating conditions gives improved results due to theincreased solubility of the coal liquefaction products. The lightliquefying solvents defined herein have a solvent density of about0.5-0.8 g./cc., and preferably about 0.6-0.7 g./cc. under practicaltemperature and pressure conditions for use in operating liquefier 28.If the solvent density is too low, then it is necessary to resort topressure to increase the density. Usually pressurized hydrogen ispreferred as a pressurizing medium, but inert gases or gaseous mixturesmay be employed such as nitrogen, argon and helium. Also, the pressureexisting in liquefier 28 may be imposed by suitable hydrostatic meanssuch as a high-pressure pump.

Suprisingly, light organic solvents are effect liquefying solvents attemperatures above their criticals. In such instances, the liquefyingsolvent is a supercritical fluid which has the necessary minimum solventdensity due to imposing pressure upon the system. When the liquefier 28is operated within 50 F. below the critical temperature of the solventor higher, then the solvent is either a supercritical fluid or hasproperties similar to a supercritical fluid. The solvent has a muchlower viscosity and a higher diffusivity, and it penetrates the coalparticles faster. Solvation temperatures between 50 F. below thecritical temperature of the liquefying solvent and l,000 F. produceunusually good results, and especially when elemental hydrogen is usedas a pressurizing gas. The presence of elemental hydrogen also increasessolvent recovery as thermal decomposition is reduced.

In instances where the solution flowing in conduit 49 contains lowboiling normally liquid liquefaction products, as well as insolubleconstituents and/or dissolved liquefaction products which are semisolidto solid at room temperature, then the low boiling products may beremoved by fraction distillation prior to removal of the insolubleconstituents and/or fractionating the semisolid to solid coalliquefaction products. As a general rule, the average molecular weightand complexity of the coal liquefaction products increase with theboiling points of the normally liquid products and with the softeningpoints of the semisolid to solid products, and products having a similarboiling point or softening point also tend to have similar physicaland/or chemical characteristics.

lt is possible to separate one or more distillate fraction of normallyliquid products by a prior art fractionating step which is not shown inthe drawings in the interest of clarity, and thereafter separate withheavy oils, semisolid and solid products into a plurality of fractionsby the method of the invention. While the fractions may differ markedlyin chemical and/or physical characteristics, the products within afraction may have similar chemical and/or physical characteristics andit is possible to produce fractions which are suitable for specific enduses. For example, low boiling normally liquid fractions may be used asfuels, and liquid fractions of higher boiling point may be catalyticallyor thermally cracked to produce low boiling distillates for use asfuels. The slurry 53 withdrawn from vessel 47 contains a highconcentration of sulfur, mineral ash and other undesirable constituents,but it is possible to use the residue remaining after flashing off thesolvent as a fuel for firing boilers and the link in areas where airpollution is not a problem. After flashing off the solvent, the heavyfraction of coal liquefaction products 72 withdrawn from vessel 67 isuseful as a solid fuel in metropolitan areas where air pollutionregulations require the use of low sulfur fuels. The fraction of coalliquefaction products of intermediate softening point withdrawn fromvessel 79 has a low sulfur content and it is useful as a solid fuel inmetropolitan areas. Additionally, vessel 79 may be operated at asufficiently elevated temperature and low solvent density to separate afraction having a softening point below 200 F. and preferably below P.which may be hydrofined and/or hydrocatalytically cracked to produceliquid fuels. The fraction 94 of light coal liquefaction productswithdrawn from vessel 92 is normally semisolid to liquid upon flashingoff the solvent, and it likewise may be fed to a conventional catalytichydrofining unit and/or catalytic or hydrocatalytic cracker to producelow boiling distillate fractions useful as fuels.

lt is possible to bypass up to two of the vessels 47, 67 and 79 ininstances where the desired end products will permit it. For example,when the solution flowing in conduit 49 contains an unobjectionableamount of insoluble constituents, vessel 47 may be bypassed and thesolution flowing in conduit 49 may be introduced directly into vessel67. If insoluble constituents are not objectionable in the heavyfraction 72, then vessel 47 may be operated under the conditionsdescribed for vessel 67 to thereby cause the separation of heavyfraction 72 and slurry phase 53 simultaneously in vessel 47, vessel 67may be bypassed, and the solution flowing in conduit 65 may beintroduced directly into vessel 79. Similarly, the heavy fractions 72and 80 may be rejected along with slurry 53 by operating vessel 47 underconditions described for vessel 79, and the solution flowing in conduit65 may be introduced directly into vessel 92. It is also possible tobypass vessel 67 and introduce the solution flowing in conduit 65directly into vessel 79, and thereby separate the insoluble materials inslurry phase 53 in vessel 47 and reject heavy phases 72 and 80 in vessel79. Still other modifications may be made in the fractionating schemeillustrated in the drawings and described herein.

The vessels 47, 67 79 and 92 are operated at a sufficiently elevatedtemperature to form a liquid-to-liquid bulk interface between theseparated fluidlike heavy fractions 53, 72, 80 and 94 and the lightersolvent-rich fractions 54, 75, 81 and 95, respectively. The minimumtemperature sufficient to form the liquid-to-liquid bulk interface willvary somewhat with the sol vent and the chemical and physical nature ofthe separated heavy fractions and the lighter solvent-rich fractions.For example, the minimum temperature of at least 400 F. is sufficientlyhigh to form the necessary liquid-to-liquid bulk interface, whichtemperature may be as high as 500650 F. with some solvents whenseparating heavy fractions. At lower fractionating temperatures, thesolvent may percipitate a fraction, but the fraction has a viscositywhereby it is not fluidlike and freely flowable from the treating zone.The fractions precipitated at lower temperature are semisolids or solidswhich tend to plug the apparatus as they are withdrawn and thuscontinuous operation is very difiicult or impossible.

The maximum temperature for operating vessel 67 at practical pressuresto separate a fraction containing coal solubilization products having asoftening point above about 400 F. is approximately the criticaltemperature of the light organic fractionating solvent, the pressurebeing adjusted simultaneously to provide a solvent density about 0.05g./cc. less than that prevailing in vessel 47. At temperatures abovethis level, the density change in the fractionating solvent is veryrapid and coal liquefaction products having lower softening point thanabout 400 F. separate along with the higher softening point materials,and this lowers the softening point of fraction 72. By operating vessel67 near the minimum fractionating temperature, it is possible toseparate a heavy fraction having a softening point in excess of about400 F.

The selection of a specific fractionating temperature between 400 F. andabout the critical temperature of the fractionating solvent provides aconvenient means of separating varying yields of heavy fractions of coalliquefaction products having high softening point and a high degree ofmolecular complexity. lnasmuch as some of the heavy constituents oftenhave objectionably characteristics for certain end uses, the inventionprovides a convenient means for removing the objectionable heavyfraction prior to recovery of the remaining lighter fractions. it isalso possible to operate vessel 47 at. a temperature closelyapproximating the minimum level for forming a liquid-to-liquid bulkinterface, and reject a small amount of heavy tarry coal liquefactionproducts along with the insoluble constituents to flux the same.Thereafter, the temperature may be raised in one or more stages to alevel approaching the maximum for separating fractions having softeningpoints of 400 F. or higher, and additional fractions having softeningpoints above 400 F. may be separated.

ln instances, for example, where the heavy fraction 72 has a softeningpoint of 400 F. or above, then vessel 79 may be operated at atemperature higher than about the critical temperature and at a solventdensity of, for example, about 0.05 g./cc. less than that prevailing invessel 67 to separate a fraction having a softening point below about400 F. Surprisingly, the critical temperature is not the maximumtemperature at which a fraction of coal liquefaction products may berecovered from the solvent. Under the proper pressure conditions, theupper temperature limit is the decomposition temperature of the solventand/or coal liquefaction products. In instances where the temperature issignificantly higher than the critical temperature of the solvent, thenthe coal fraction usually has a lower softening point, such as below lF.

The fractionating vessel 92 is preferably operated above the criticaltemperature of the organic fractionating solvent to separate theremaining dissolved coal liquefaction products as a heavy phase 94 fromthe lighter phase 95 of solvent. Vessel 92 may be operated atessentially the same pressure as vessel 79, and the temperature may beincreased to a value such that the density of the solvent at theprevailing pressure is about 0.2 g./cc. or lower. Under theseconditions, the solvent is phased out and separates from the remainingcoal liquefaction products, which appear at the bottom of fractionatingvessel 92 as fraction 94. Fraction 94 is usually a heavy liquid orsemisolid material at room temperature.

It is apparent from the foregoing discussion that, when operatingvessels 47, 67, 79 and 92 at approximately the same pressure with theexception of line and heat exchanger drop, the temperature may beincreased in each successive vessel to provide successively lowersolvent densities whereby a phase separation occurs in each vessel. Theheat energy required to increase the temperature in the vessels iseasily recovered by heat exchange with the returning solvent stream aspreviously described. When operating vessels 47, 67, 79 and 92 atsubstantially the same temperature and making solvent density changestherein by adjusting the pressure, the energy required for adjusting thesolvent densities in vessels 47, 67, 79 and 92 to the necessarysuccessively lower levels for phase separation cannot be recoveredconveniently.

The following specification examples further illustrate the invention.

EXAMPLE 1 One hundred pounds per hour of Oklahoma Stigler seam coalcontaining 12.] weight percent of ash, 25.8 weight percent of volatilematter and 62.1 weight percent of fixed carbon, and having a particlesize of 65 mesh is withdrawn from vessel l6 and introduced into mixer12. One thousand pounds per hour of pyridine is withdrawn from vessel 11and introduced into mixer 12 where it is admixed with the incoming coalfeed. The resultant slurry is withdrawn via conduit 20, pressurized to3,500 p.s.i.g. by pump 21, and admixed with 2 pounds per hour ofhydrogen introduced therein via conduit 30. The slurry is then passed toheater 22 where the temperature is raised to 675 F. and introduced intoliquefier 28 via conduit 27. The average residence time in the liquefier28 is 1 hour and the solvent density is 0.62 g./cc.

The mixture of insoluble coal and pyridine solution of liquefied coal iswithdrawn from liquefier 28 via conduit 35 and introduced into bulkinsoluble coal separator 36 where the insoluble constituents are allowedto settle as a fluidlike phase 37 and are withdrawn via conduit 39. Theseparator 36 operates at substantially the same temperature and pressureconditions as liquefier 28. The insoluble coal fraction withdrawn viaconduit 39 contains approximately 50 pounds per hour of insoluble coaland ash constituents and 50 pounds per hour of pyridine. The pyridine isflashed from the insoluble constituents, the vapor is condensed, and theliquid pyridine is recycled to vessel 11. The insoluble coal fractioncontains 23.0 weight percent of ash, 23.6 weight percent of volatilematter and 53.4 weight percent of fixed carbon.

The solution 38 remaining as the light phase in separator 36 containsapproximately 2 pounds per hour of suspended insoluble material which islargely present in the form of micron size particles. The solution 38 ispassed via conduit 41 through heat exchanger 46, and its temperature isadjusted so that after passing through valve 44 and reducing thepressure to 1,000 p.s.i.g. the temperature of the solution is about 640F. The solution is then introduced into gas separating vessel 61, fromwhich released gases such as hydrogen and light hydrocarbons are removedvia conduit 62. The degassed solution is then withdrawn from vessel 61and passed via conduit 49 into deashing-fractionating vessel 47.

Vessel 47 operates at a solvent density of about 0.53 g.lcc., and aheavy slurry phase 53 separates and is withdrawn via conduit 55 at therate of 12 pounds per hour. The slurry 53 contains the ash mineralbrought into vessel 47, about 4 pounds per hour of separated previouslydissolved heavy coal liquefaction products, and 6 pounds per hour ofpyridine.

The remaining soluble liquefied coal products in the lighter phase 54,now free of ash mineral, are withdrawn via conduit 65, passed throughheat exchanger 66, and then introduced into fractionating vessel 67 at atemperature of 660 F. and at substantially the pressure prevailing invessel 47. The solvent density in vessel 67 is about 0.49 g.lcc. A heavyfluidlike phase 72 separates in the bottom of vessel 67 and is readilywithdrawn therefrom via conduit 73 at the rate of 25 pounds per hour ofdeashed coal containing an equal weight of pyridine. Upon flashing offthe pyridine solvent, the residue has a softening point in excess of 400F., an ash content of 22.3 weight percent, and a fixed carbon content of76.8 weight percent.

The solution of remaining liquefied coal products existing as solventrich phase 75 is withdrawn via conduit 77, passed through heat exchanger78 where it is heated to 680 F., and is then introduced intofractionating vessel 79. The pressure in fractionating vessel 79 isabout 975 p.s.i.g., and the solvent density is about 0.35 g./cc. Theintermediate fraction of coal liquefaction products which separates asheavy phase 80 in the bottom of vessel 79 is fluidlike and is withdrawnvia conduit 87 at the rate of about 10 pounds of coal liquefactionproducts per hour along with 20 pounds per hour of pyridine. Uponflashing off the pyridine, the residue has a softening point of 200 F.,an ash content of 0.81 weight percent, a volatile matter content of 40.9weight percent, and a fixed carbon content of 8.3 weight percent.

The solvent-rich phase 81 is withdrawn from vessel 79 via conduit 90,passed through heat exchanger 91 and heater 93 where the temperature israised to 735 F., and introduced into fractionating vessel 92. Thevessel 92 operates at substantially the same pressure as vessel 79 andthe solvent density is 0.18 g./cc. A fluid heavy phase containing thelightest portion of the liquefied coal products separates in the bottomof vessel 92 and is removed therefrom via conduit 101 at a rate ofpounds per hour along with pounds per hour of pyridine. Upon evaporationand recover of the pyridine, the resultant residue has an ash content of0.38 weight percent, a volatile matter content of 66.1 weight percent,and a fixed carbon content of 33.5 weight percent.

The solvent-rich phase 95 in the upper portion of vessel 92 contains99.3 weight percent of pyridine. It is removed from the top of vessel 92via conduit 64, passed successively through heat exchangers 91, 78 and66 in heat exchange relationship with the solvent-rich phases flowing inconduits 90, 77 and 65 to recover its heat content, then through heatexchanger 103 to reduce its temperature sufficiently to produce coolpyridine solvent, and the cooled solvent is introduced into vessel 11awaiting recycle. The pyridine flashed from the heavy fractions 53, 72,80 and 94 is recovered by condensation and returned to surge vessel 11via conduit 8, and makeup solvent likewise is supplied to vessel 11 viaconduit 8 as required.

EXAMPLE 11 Two thousand grams of Oklahoma Stigler seam coal having aparticle size of -65 mesh, a volatile matter content of 25.8 weightpercent, a fixed carbon content of 63.0 weight percent, a sulfur contentof 2.12 weight percent, and an ash content of 12.1 weight percent wastreated with 6,000 grams of anthracene oil at 400 C. for 1 hour in thepresence of hydrogen at a pressure of 625 p.s.i.g. More than 80 percentof the coal was dissolved. The solution was centrifuged to removeinsoluble matter and the anthracene oil was removed by vacuumdistillation to produce a deashed and desolvated coal product whichanalyzed 0.7 weight percent of ash, 0.61 weight percent of sulfur, 36.6weight percent of volatile matter, and 62.7 weight percent of fixedcarbon.

One thousand grams of the above prepared antracene oilfree deashed coalproduct was placed in a pressure vessel together with 20,000 grams ofbenzene. The pressure of the contents of the pressure vessel wasmaintained at approximately 1,000 p.s.i.g. and the temperature wasraised periodically to successively higher levels. At each temperaturelevel, a fluidlike heavy phase containing about 50 weight percent coalliquefaction products and about 50 weight percent benzene separated andwas withdrawn from the bottom of the pressure vessel. The results aregiven in the following table:

EXAMPLE in One thousand grams of the deashed and desolvated coal productprepared in accordance with example 11 is introduced 5 into a pressurevessel along with 5,000 grams of normal hex- 10 ture the density of thehexane solvent is 0.39 g./cc., a fluidlike heavy phase forms in thebottom of the pressure vessel consisting of equal parts by weight ofhexane and coal liquefaction products. After withdrawing the heavy phasefrom the pressure vessel and flashing off the hexane, the residue has avolatile matter content of 35.8 weight percent.

Upon raising the temperature of the contents of the pressure vessel to520 F., at which temperature the density of the hexane solvent is 0.33g./cc. a fluidlike heavy phase forms in the bottom of the pressurevessel consisting of approximately equal parts by weight of hexane andintermediate coal liquefaction products. After withdrawing the fractionof intermediate coal liquefication products from the pressure vessel andflashing off the solvent, the residue has a volatile matter content of 5l .8 weight percent.

The temperature of the contents of the pressure vessel is further raisedto 570 F., at which temperature the hexane solvent density is 0.27g./cc., and a fluidlike heavy phase of coal liquefaction productsseparates which has a hexane content of about 50 percent. Uponwithdrawing this heavy phase and flashingoff the hexane, the residue hasa volatile matter content of 74.7 weight percent.

The temperature of the contents of the pressure vessel is further raisedto 650 F., at which temperature the hexane density is 0.20 g./cc., and afluidlike phase of coal liquefaction products of very light characterseparates. Upon withdrawing this phase from the pressure vessel andflashing off the hexane solvent, the residue has a volatile mattercontent of 84.4 weight percent.

When desired, the various light organic solvents which are disclosedherein as being suitable for both liquefaction and fractionation of coalmay be substituted for pyridine as the solvent in example 1 to therebyobtain comparable results. Similarly, the various light organic solventswhich are disclosed herein as being suitable for either liquefaction andfractionation or fractionation alone of coal may be substituted forbenzene and hexane as a fractionating solvent in examples II and Ill,respectively, to obtain comparable results.

1 claim: 1. A method of fractionating products of coal liquefaction intoa plurality of fractions comprising:

treating an organic-solvent solution of products of coal liquefaction ina treating zone at an elevated temperature and pressure to separate afluidlike first heavy fraction of coal liquefaction products from alighter first solvent-rich phase containing dissolved coal liquefactionproducts,

said solution containing initially at least two parts by weight of theorganic solvent for each part by weight of the dissolved coalliquefaction products,

the organic solvent consisting essentially of at least one substancehaving a critical temperature below 800 F. selected from the groupconsisting of aromatic hydrocarbons having a single benezene nucleus andnormally boiling points below about 310 F., cycloparaffin hydrocarbonshaving normal boiling points below about 310 F., open chain mono-olefinhydrocarbons having normal boiling POlNTS BELOW ABOUT 310 F., open chainsaturated hydrocarbons having normal boiling points below about 310 F.,mono-, di-, and tri-open chain amines, carbocyclic amines having amonocyclic structure, heterocyclic amines, and phenol and its homologs,

said solution being treated at a temperature of at least 400 F. and thetemperature being sufficiently elevated to form a liquid-to-liquid bulkinterface between the first heavy fraction and the first solvent richphase,

the temperature and pressure being adjusted to provide a solvent densityin the treating zone of less than about 0.55 g./cc., the solvent densitybeing sufficient low to separate the first heavy fraction from the firstsolvent-rich phase and sufficiently high to retain the remaining coalliquefaction products in solution in the first solvent-rich phase,

the first heavy fraction having a viscosity under the temperature andpressure conditions existing in the treating zone whereby it is flowablefrom the treating zone, and

withdrawing the first heavy fraction from the treating zone.

2. The method of claim 1 wherein the organic solvent is selected fromthe group consisting of pyridine, benzene and hexane.

3. The method of claim 1 wherein said solution contains initially finelydivided insoluble material derived from coal during liquefaction,

the temperature and pressure are adjusted to provide a solvent densityin the treating zone of about 0.35-0.55 g./cc. when separating the firstheavy fraction,

a body of slurry containing the insoluble material and the first heavyfraction is separated in a lower portion of the treating zone, the bodyof slurry containing the first heavy fraction in an amount to flux theinsoluble material present therein under the temperature and pressureconditions existing in the treating zone, and

the slurry is withdrawn from the treating zone.

4. The method of claim 1 wherein the first solvent-rich phase is furthertreated in a treating zone under elevated temperature and pressureconditions to separate at least one additional fluidlike heavy fractionof coal liquefaction products including a fluidlike final heavy fractionof residual coal liquefaction products which is separated from a lighterorganic-solvent phase,

the temperature and pressure being adjusted to provide a solvent densityin the treating zone during separation of the final heavy fraction notgreater than about 0.15-0.20 g./cc. and sufficiently low to separate theresidual coal liquefaction products from the organic-solvent phase,

the final heavy fraction having a viscosity under the temperature andpressure conditions existing in the treating zone during the separationthereof whereby it is flowable from the treating zone, and

withdrawing the final heavy fraction of residual coal liquefactionproducts from the treating zone.

5. The method of claim 4 wherein the organic solvent is selected fromthe group consisting of pyridine, benzene and hexane.

6. The method of claim 4 wherein said solution contains initially finelydivided insoluble material derived from coal during liquefaction, thetemperature and pressure are adjusted to provide a solvent density inthe treating zone of about 0.35-0.55 g./cc. when separating the firstheavy fraction, a body of slurry containing the insoluble material andthe first heavy fraction is separated in a lower portion of the treatingzone, the body of the slurry contains the heavy fraction in an amount toflux the insoluble material present therein under the temperature andpressure conditions existing in the treat ing zone, and the slurry iswithdrawn from the treating zone.

7. The method of claim 4 wherein the pressure in the treating zoneduring separation of the first heavy fraction and at least oneadditional heavy fraction including the final heavy fraction isapproximately the same, and the temperature of the solvent is adjustedto provide the desired solvent density for separation of at least oneadditional heavy fraction including the final heavy fraction.

8. The method of claim 4 wherein the separated organic-solvent phase iswithdrawn from the treating zone and passed in heat exchangerelationship with at least one relatively cool solvent-rich phase toraise the temperature thereof prior to treating the same at elevatedtemperature and pressure in the treating zone.

9. The method of claim 4 wherein at least one fluidlike intermediateheavy fraction of coal liquefaction products is obtained by treating thefirst solvent-rich phase in at least one treating zone under elevatedtemperature and pressure conditions providing a solvent density thereinwhich is less than that existing in the treating zone when separatingthe first heavy fraction and greater than about 0.15-0.20 g./cc.,

at least one intermediate heavy fraction separated by this treatmenthaving a viscosity under the temperature and pressure conditionsexisting in the treating zone whereby it is freely flowable therefrom,and

withdrawing at least one intermediate heavy fraction from at least onetreating zone.

10. The method of claim 9 wherein said solution contains initiallyfinely divided insoluble material derived from coal during liquefaction,the temperature and pressure are adjusted to provide a solvent densityin the treating zone of about 0.350.55 g./cc. when separating the firstheavy fraction, a body of slurry containing the insoluble material andthe first heavy fraction is separated in a lower portion of the treatingzone, the body of slurry contains the heavy fraction in an amount toflux the insoluble material present therein under the temperature andpressure conditions existing in the treating zone, and the slurry iswithdrawn from the treating zone.

11. The method of claim 10 wherein the pressure in the treating zoneduring separation of the first heavy fraction and at least oneadditional heavy fraction including the final heavy fraction isapproximately the same, and the temperature of the solvent is adjustedto provide the desired solvent density for separation of at least oneadditional heavy fraction including the final heavy fraction.

12. The method of claim 11 wherein the separated organicsolvent phase iswithdrawn from the treating zone and passed in heat exchangerelationship with at least one relatively cool solvent-rich phase toraise the temperature thereof prior to treating the same at elevatedtemperature and pressure in the treating zone.

13. A process for liquefying and fractionating coal comprisingintimately contacting coal in particulate form with an organic solventin a coal liquefaction zone to produce a solution containing products ofcoal liquefaction and suspended finely divided insoluble material.

the organic solvent consisting essentially of at least one sub stancehaving a critical temperature below 800 F. selected from the groupconsisting of aromatic hydrocarbons having a single benzene nucleus andnormal boiling points below about 3l0 F., cycloparaffin hydrocarbonshaving normal boiling points below about 310 F., mono-, di-, andtri-straight chain amines, carbocyclic amines hav ing a monocyclicstructure, heterocyclic amines, and phenol and its homologs,

the coal being contacted with the solvent in the liquefaction zone at atemperature of about 550-] ,000 F. and under a pressure of about 400-]0,000 p.s.i.a., said temperature being below the solvent decompositiontemperature and the solution thus produced containing at least two partsby weight of the organic solvent for each part by weight of the coalliquefaction products and having finely divided insoluble materialtherein, the temperature and pressure in the liquefaction zone beingadjusted to provide a solvent density of at least 0.5 g./cc.,

withdrawing the organic-solvent solution of coal liquefaction productsfrom the liquefaction zone and introducing it into a first treatingzone,

treating the organic-solvent solution of coal liquefaction products inthe first treating zone at an elevated temperature and pressure toseparate a fluidlike first heavy fraction containing coal liquefactionproducts and said finely divided insoluble material and a lighter firstorganic solvent-rich phase containing dissolved coal liquefactionproducts,

said solution being treated in the first treating zone at a temperatureof at least 400 F. and the temperature being sufficiently elevated toform a liquid-to-liquid bulk interface between the first heavy fractionand the first solvent-rich phase,

the temperature and pressure being adjusted to provide a solvent densityof less than about 0.55g./cc. in the first treating zone, the solventdensity in the first treating zone being less than the solvent densityat which the coal was contacted with the solvent in the coalliquefaction zone and sufficiently low to separate the first heavyfraction from the first solvent-rich phase and sufficiently high toretain the remaining coal liquefaction products in the firstsolvent-rich phase,

the first heavy fraction having a viscosity under the temperature andpressure conditions existing in the first treating zone whereby it isflowable from the first treating zone, and

withdrawing the first heavy fraction from the first treating zone.

14. The process of claim 13 wherein said organic solvent is selectedfrom the group consisting of pyridine and benzene.

15. The process of claim 13 wherein said organic solvent solution ofcoal liquefaction products is withdrawn from the liquefaction zone andintroduced into an insoluble coal-separating zone,

the said solution is maintained in the insoluble coal-separating zone atapproximately the same temperature and pressure as exist in theliquefaction zone and for a residence time sufficient to separate aheavy slurry phase which contains a major amount of the insolublematerial and a lighter phase which contains dissolved coal liquefactionproducts and some insoluble material, the heavy slurry phase beingflowable under the temperature and pressure conditions existing in theinsoluble coal separating zone,

the heavy slurry phase is withdrawn from the insoluble coalseparatingzone, and

the lighter phase containing dissolved coal liquefaction products andsome insoluble material is withdrawn from the coal-separating zone andintroduced into the first treating zone.

16. The process of claim 13 wherein the residence time of said solutionin the first treating zone is sufficient to settle insoluble materialtherefrom, and

the temperature and pressure in the first treating zone are adjusted toprovide a solvent density of about 0.35-0.55 g./cc. and sufficiently lowto separate coal liquefaction products from said solution in an amountto flux the settled insoluble material whereby it may be withdrawn as afluidlike phase.

17. The process of claim 13 wherein said first solvent-rich phase iswithdrawn from the first treating zone and is introduced into at leastone additional treating zone including a final treating zone,

the first solvent-rich phase is further treated under elevatedtemperature and pressure conditions to separate at least one additionalfluidlike heavy fraction of coal liquefaction products including afluidlike final heavy fraction of residual coal liquefaction productswhich is separated in the final treating zone from a lighter organicsolvent phase,

the temperature and pressure are adjusted to provide a solvent densityin the final treating zone during separation of the final heavy fractionnot greater than about 0. 1 5-020 g./cc. and sufficiently low toseparate the residual coal liquefaction products from theorganic-solvent phase,

the final heavy fraction has a viscosity under the temperature andpressure conditions existing in the treating zone during the separationthereof whereby it is flowable from the treating zone, and

the final heavy fraction of residual coal liquefaction products iswithdrawn from the treating zone.

18. The process of claim 17 wherein the organic solvent is selected fromthe group consisting of pyridine and benzene.

19. The process of claim 17 wherein the pressure in the treating zonesduring separation of the heavy fractions is approximately the same, andthe temperature of the solvent is adjusted to provide the desiredsolvent density in the treating zones for separation of the heavyfractions.

20. The process of claim 17 wherein the separated organicsolvent phaseis withdrawn from the final treating zone and is passed in heat exchangerelationship with at least one relatively cool solvent-rich phase toraise the temperature thereof prior to treating the same at elevatedtemperature and pressure in at least one treating zone.

21. The process ofclaim 17 wherein at least one fluidlike intermediateheavy fraction of coal liquefaction products is obtained by treating thefirst solvent-rich phase in at least one treating zone under elevatedtemperature and pressure conditions providing a solvent density thereinwhich is less than that existing in the treating zone when separatingthe first heavy fraction and greater than about 0.15-0.20 g./cc.,

at least one intermediate heavy fraction separated by this treatmenthaving a viscosity under the temperature and pressure conditionsexisting in the treating zone whereby it is freely flowable therefrom,and

withdrawing at least one intermediate heavy fraction from at least onetreating zone.

22. The process of claim 21 wherein the pressure in the treating zonesduring separation of the heavy fractions is approximately the same, andthe temperature of the solvent is adjusted to provide the desiredsolvent density in the treating zones for separation of the heavyfractions.

23. The process of claim 22 wherein the separated organicsolvent phaseis withdrawn from the final treating zone and is passed in heat exchangerelationship with at least one relatively cool solvent-rich phase toraise the temperature thereof prior to treating the same at elevatedtemperature and pressure in at least one treating zone.

24. A method of separating suspended finely divided insoluble materialfrom products of'coal liquefaction comprising introducing anorganic-solvent solution of products of coal liquefaction into asettling zone having upper and lower portions,

said solution containing at least two parts by weight of organic solventfor each part by weight of dissolved coal liquefaction products, andhaving therein suspended fine- 1y divided insoluble material derivedfrom the coal during liquefaction,

the lower portion of the settling zone having therein a rela tivelyheavy fluidlike body of slurry containing said insoluble material in amarkedly higher concentration than present in said solution initially,

the upper portion of the settling zone having therein a relatively tightbody of an organic-solvent solution of coil liquefaction productscontaining said insoluble material in a substantially lowerconcentration than present in said solution initially,

said solution being injected into the lower portion of the settling zonebeneath the surface of the body of slurry and passing upward therefrominto the upper portion of the settling zone,

said finely divided insoluble material being agglomerated and retainedin the body of slurry,

withdrawing slurry from the lower portion of the settling zone, and

withdrawing from the upper portion of the settling zone anorganic-solvent solution of coal liquefaction products having asubstantially lower concentration of insoluble material than present insolution initially.

25. The method of claim 24 wherein the body of slurry contains finelydivided insoluble material fluxed with a fraction of coal liquefactionproducts and organic solvent, and the slurry has a viscosity whereby itmay be withdrawn from the settling zone as a fluidlike phase.

26. The method of claim 24 wherein a fraction of coal liquefactionproducts is separated from said solution and deposited on the suspendedparticles of insoluble material whereby the particles of insolublematerial may be agglomerated in the settling zone.

27. The method of claim 24 wherein the organic solvent comprises atleast one substance having a critical temperature below 800 F. selectedfrom the group consisting of aromatic Patent No.

UNITED STATES PATENT OFFICE CERTIFICATE OF CGRRECTION Inventor(s) Column7, line 4-5, line 52, line 14, line 28, line 3, line 67, line 1, line17, line 1, line 15,

Column 8,

Column 9,

Column 10,

Column Column Dated September 21, 1971 Jack W. Roach It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

"aver" should read average "penetrate" should read penetrates"hetercyclic" should read heterocyclic "310? E." should read 310 F."reaction" should read reactor "fraction should read fractional"fractionfshould read fractions "link" should read like "specification"should read specific "recover" should read recovery in the tableappearing at the bottom of the column the print is not discernible andshould read:

Withdrawn heavy phase (solvent free) Weight Weight Solvent percentWeight percent density, Weight, volatile percent fixed Temperature, F.g./cc. g. matter ash carbon 535 0.55 260 p 30.0 0.3 68.4 610 0.29 40032.2 0.3 69.0 660 0.19 170 33.0 0.l 68.0 720 0.15 150 36. 9 0.l' 63.1

Column 14, line 67, "POINTS BELOW ABOUT" should read points below about[Column 15, line 10, "sufficient" should read sufficiently Column 17,line 73, "0 15" should read 0.15

Signed and sealed this 25th day of April 1972. r

(SEAL) Attest:

EDWARD MFLETCHER Attesting Officer QM PO-IOSO (10-69) ROBERT GOTTSCHALKCommissioner of Patents L USCOMM-DC 60376-P69 i us GOVERNMENT mmrmsOrncz; 1969 0-36b-l8l

2. The method of claim 1 wherein the organic solvent is selected fromthe group consisting of pyridine, benzene and hexane.
 3. The method ofclaim 1 wherein said solution contains initially finely dividedinsoluble material derived from coal during liquefaction, thetemperature and pressure are adjusted to provide a solvent density inthe treating zone of about 0.35-0.55 g./cc. when separating the firstheavy fraction, a body of slurry containing the insoluble material andthe first heavy fraction is separated in a lower portion of the treatingzone, the body of slurry containing the first heavy fraction in anamount to flux the insoluble material present therein under thetemperature and pressure conditions existing in the treating zone, andthe slurry is withdrawn from the treating zone.
 4. The method of claim 1wherein the first solvent-rich phase is further treated in a treatingzone under elevated temperature and pressure conditions to separate atleast one additional fluidlike heavy fraction of coal liquefactionproducts including a fluidlike final heavy fraction of residual coalliquefaction products which is separated from a lighter organic-solventphase, the temperature and pressure being adjusted to provide a solventdensity in the treating zone during separation of the final heavyfraction not greater than about 0.15-0.20 g./cc. and sufficieNtly low toseparate the residual coal liquefaction products from theorganic-solvent phase, the final heavy fraction having a viscosity underthe temperature and pressure conditions existing in the treating zoneduring the separation thereof whereby it is flowable from the treatingzone, and withdrawing the final heavy fraction of residual coalliquefaction products from the treating zone.
 5. The method of claim 4wherein the organic solvent is selected from the group consisting ofpyridine, benzene and hexane.
 6. The method of claim 4 wherein saidsolution contains initially finely divided insoluble material derivedfrom coal during liquefaction, the temperature and pressure are adjustedto provide a solvent density in the treating zone of about 0.35-0.55g./cc. when separating the first heavy fraction, a body of slurrycontaining the insoluble material and the first heavy fraction isseparated in a lower portion of the treating zone, the body of theslurry contains the heavy fraction in an amount to flux the insolublematerial present therein under the temperature and pressure conditionsexisting in the treating zone, and the slurry is withdrawn from thetreating zone.
 7. The method of claim 4 wherein the pressure in thetreating zone during separation of the first heavy fraction and at leastone additional heavy fraction including the final heavy fraction isapproximately the same, and the temperature of the solvent is adjustedto provide the desired solvent density for separation of at least oneadditional heavy fraction including the final heavy fraction.
 8. Themethod of claim 4 wherein the separated organic-solvent phase iswithdrawn from the treating zone and passed in heat exchangerelationship with at least one relatively cool solvent-rich phase toraise the temperature thereof prior to treating the same at elevatedtemperature and pressure in the treating zone.
 9. The method of claim 4wherein at least one fluidlike intermediate heavy fraction of coalliquefaction products is obtained by treating the first solvent-richphase in at least one treating zone under elevated temperature andpressure conditions providing a solvent density therein which is lessthan that existing in the treating zone when separating the first heavyfraction and greater than about 0.15-0.20 g./cc., at least oneintermediate heavy fraction separated by this treatment having aviscosity under the temperature and pressure conditions existing in thetreating zone whereby it is freely flowable therefrom, and withdrawingat least one intermediate heavy fraction from at least one treatingzone.
 10. The method of claim 9 wherein said solution contains initiallyfinely divided insoluble material derived from coal during liquefaction,the temperature and pressure are adjusted to provide a solvent densityin the treating zone of about 0.35-0.55 g./cc. when separating the firstheavy fraction, a body of slurry containing the insoluble material andthe first heavy fraction is separated in a lower portion of the treatingzone, the body of slurry contains the heavy fraction in an amount toflux the insoluble material present therein under the temperature andpressure conditions existing in the treating zone, and the slurry iswithdrawn from the treating zone.
 11. The method of claim 10 wherein thepressure in the treating zone during separation of the first heavyfraction and at least one additional heavy fraction including the finalheavy fraction is approximately the same, and the temperature of thesolvent is adjusted to provide the desired solvent density forseparation of at least one additional heavy fraction including the finalheavy fraction.
 12. The method of claim 11 wherein the separatedorganic-solvent phase is withdrawn from the treating zone and passed inheat exchange relationship with at least one relatively coolsolvent-rich phase to raise the temperature thereof prior to treatingthe same aT elevated temperature and pressure in the treating zone. 13.A process for liquefying and fractionating coal comprising intimatelycontacting coal in particulate form with an organic solvent in a coalliquefaction zone to produce a solution containing products of coalliquefaction and suspended finely divided insoluble material. theorganic solvent consisting essentially of at least one substance havinga critical temperature below 800* F. selected from the group consistingof aromatic hydrocarbons having a single benzene nucleus and normalboiling points below about 310* F., cycloparaffin hydrocarbons havingnormal boiling points below about 310* F., mono-, di-, and tri-straightchain amines, carbocyclic amines having a monocyclic structure,heterocyclic amines, and phenol and its homologs, the coal beingcontacted with the solvent in the liquefaction zone at a temperature ofabout 550-1,000* F. and under a pressure of about 400-10,000 p.s.i.a.,said temperature being below the solvent decomposition temperature andthe solution thus produced containing at least two parts by weight ofthe organic solvent for each part by weight of the coal liquefactionproducts and having finely divided insoluble material therein, thetemperature and pressure in the liquefaction zone being adjusted toprovide a solvent density of at least 0.5 g./cc., withdrawing theorganic-solvent solution of coal liquefaction products from theliquefaction zone and introducing it into a first treating zone,treating the organic-solvent solution of coal liquefaction products inthe first treating zone at an elevated temperature and pressure toseparate a fluidlike first heavy fraction containing coal liquefactionproducts and said finely divided insoluble material and a lighter firstorganic solvent-rich phase containing dissolved coal liquefactionproducts, said solution being treated in the first treating zone at atemperature of at least 400* F. and the temperature being sufficientlyelevated to form a liquid-to-liquid bulk interface between the firstheavy fraction and the first solvent-rich phase, the temperature andpressure being adjusted to provide a solvent density of less than about0.55g./cc. in the first treating zone, the solvent density in the firsttreating zone being less than the solvent density at which the coal wascontacted with the solvent in the coal liquefaction zone andsufficiently low to separate the first heavy fraction from the firstsolvent-rich phase and sufficiently high to retain the remaining coalliquefaction products in the first solvent-rich phase, the first heavyfraction having a viscosity under the temperature and pressureconditions existing in the first treating zone whereby it is flowablefrom the first treating zone, and withdrawing the first heavy fractionfrom the first treating zone.
 14. The process of claim 13 wherein saidorganic solvent is selected from the group consisting of pyridine andbenzene.
 15. The process of claim 13 wherein said organic solventsolution of coal liquefaction products is withdrawn from theliquefaction zone and introduced into an insoluble coal-separating zone,the said solution is maintained in the insoluble coal-separating zone atapproximately the same temperature and pressure as exist in theliquefaction zone and for a residence time sufficient to separate aheavy slurry phase which contains a major amount of the insolublematerial and a lighter phase which contains dissolved coal liquefactionproducts and some insoluble material, the heavy slurry phase beingflowable under the temperature and pressure conditions existing in theinsoluble coal separating zone, the heavy slurry phase is withdrawn fromthe insoluble coal-separating zone, and the lighter phase containingdissolved coal liquefaction products and some insoluble material iswithdrawn From the coal-separating zone and introduced into the firsttreating zone.
 16. The process of claim 13 wherein the residence time ofsaid solution in the first treating zone is sufficient to settleinsoluble material therefrom, and the temperature and pressure in thefirst treating zone are adjusted to provide a solvent density of about0.35-0.55 g./cc. and sufficiently low to separate coal liquefactionproducts from said solution in an amount to flux the settled insolublematerial whereby it may be withdrawn as a fluidlike phase.
 17. Theprocess of claim 13 wherein said first solvent-rich phase is withdrawnfrom the first treating zone and is introduced into at least oneadditional treating zone including a final treating zone, the firstsolvent-rich phase is further treated under elevated temperature andpressure conditions to separate at least one additional fluidlike heavyfraction of coal liquefaction products including a fluidlike final heavyfraction of residual coal liquefaction products which is separated inthe final treating zone from a lighter organic solvent phase, thetemperature and pressure are adjusted to provide a solvent density inthe final treating zone during separation of the final heavy fractionnot greater than about 0.15-0.20 g./cc. and sufficiently low to separatethe residual coal liquefaction products from the organic-solvent phase,the final heavy fraction has a viscosity under the temperature andpressure conditions existing in the treating zone during the separationthereof whereby it is flowable from the treating zone, and the finalheavy fraction of residual coal liquefaction products is withdrawn fromthe treating zone.
 18. The process of claim 17 wherein the organicsolvent is selected from the group consisting of pyridine and benzene.19. The process of claim 17 wherein the pressure in the treating zonesduring separation of the heavy fractions is approximately the same, andthe temperature of the solvent is adjusted to provide the desiredsolvent density in the treating zones for separation of the heavyfractions.
 20. The process of claim 17 wherein the separatedorganic-solvent phase is withdrawn from the final treating zone and ispassed in heat exchange relationship with at least one relatively coolsolvent-rich phase to raise the temperature thereof prior to treatingthe same at elevated temperature and pressure in at least one treatingzone.
 21. The process of claim 17 wherein at least one fluidlikeintermediate heavy fraction of coal liquefaction products is obtained bytreating the first solvent-rich phase in at least one treating zoneunder elevated temperature and pressure conditions providing a solventdensity therein which is less than that existing in the treating zonewhen separating the first heavy fraction and greater than about0.15-0.20 g./cc., at least one intermediate heavy fraction separated bythis treatment having a viscosity under the temperature and pressureconditions existing in the treating zone whereby it is freely flowabletherefrom, and withdrawing at least one intermediate heavy fraction fromat least one treating zone.
 22. The process of claim 21 wherein thepressure in the treating zones during separation of the heavy fractionsis approximately the same, and the temperature of the solvent isadjusted to provide the desired solvent density in the treating zonesfor separation of the heavy fractions.
 23. The process of claim 22wherein the separated organic-solvent phase is withdrawn from the finaltreating zone and is passed in heat exchange relationship with at leastone relatively cool solvent-rich phase to raise the temperature thereofprior to treating the same at elevated temperature and pressure in atleast one treating zone.
 24. A method of separating suspended finelydivided insoluble material from products of coal liquefaction comprisingintroducing an organic-solvent sOlution of products of coal liquefactioninto a settling zone having upper and lower portions, said solutioncontaining at least two parts by weight of organic solvent for each partby weight of dissolved coal liquefaction products, and having thereinsuspended finely divided insoluble material derived from the coal duringliquefaction, the lower portion of the settling zone having therein arelatively heavy fluidlike body of slurry containing said insolublematerial in a markedly higher concentration than present in saidsolution initially, the upper portion of the settling zone havingtherein a relatively tight body of an organic-solvent solution of coilliquefaction products containing said insoluble material in asubstantially lower concentration than present in said solutioninitially, said solution being injected into the lower portion of thesettling zone beneath the surface of the body of slurry and passingupward therefrom into the upper portion of the settling zone, saidfinely divided insoluble material being agglomerated and retained in thebody of slurry, withdrawing slurry from the lower portion of thesettling zone, and withdrawing from the upper portion of the settlingzone an organic-solvent solution of coal liquefaction products having asubstantially lower concentration of insoluble material than present insolution initially.
 25. The method of claim 24 wherein the body ofslurry contains finely divided insoluble material fluxed with a fractionof coal liquefaction products and organic solvent, and the slurry has aviscosity whereby it may be withdrawn from the settling zone as afluidlike phase.
 26. The method of claim 24 wherein a fraction of coalliquefaction products is separated from said solution and deposited onthe suspended particles of insoluble material whereby the particles ofinsoluble material may be agglomerated in the settling zone.
 27. Themethod of claim 24 wherein the organic solvent comprises at least onesubstance having a critical temperature below 800* F. selected from thegroup consisting of aromatic hydrocarbons having a single benzenenucleus and normal boiling points below about 310* F., cycloparaffinhydrocarbons having normal boiling points below about 310* F., openchain mono-olefin hydrocarbons having normal boiling points below about310* F., open chain saturated hydrocarbons having normal boiling pointsbelow about 310* F., mono-, di-, and tri-open chain amines, carbocyclicamines having a monocyclic structure, heterocyclic amines and phenol andits homologs.
 28. The method of claim 27 wherein the organic solvent isselected from the group consisting of pyridine, benzene and hexane.